/Engine/Plugins/Online/OnlineSubsystem/Source/Public/OnlineSubsystem.h
Determine if the subsystem for a given interface is enabled by config and command line
true if the subsystem is enabled by config
static bool IsEnabled ( const [FName](API\Runtime\Core\UObject\FName) & SubsystemName, const [FName](API\Runtime\Core\UObject\FName) & InstanceName )